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Home  >>  CBSE XII  >>  Math  >>  Model Papers
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Show that the function = 2x - | x | is continuous at x = 0.

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Toolbox:
  • If $f$ is a real function on a subset of the real numbers and $c$ a point in the domain of $f$, then $f$ is continous at $c$ if $\lim\limits_{x\to c} f(x) = f(c)$.
  • Every polynomial function $f(x)$ is continous.
Step 1:
Let $f(x)=2x-\mid x\mid$
We have $f(x)=2x-\mid x\mid$
$\Rightarrow f(x)=\left\{\begin{array} {1 1}2x-(-x)&if\;x<0\\2x-(x)&if\;x>0\end{array}\right.$
Continuity at $x=0$
We have LHL as
$\lim\limits_{x\to 0^-}f(x)=\lim\limits_{x\to 0^-}2x+x$
$\Rightarrow 0$
Step 2:
We have RHL as
$\lim\limits_{x\to 0^+}f(x)=\lim\limits_{x\to 0^+}2x-x$
$\Rightarrow 0$
Since the LHL =RHL,the given function $2x-\mid x\mid $ is continuous at $x=0$
answered Oct 3, 2013 by sreemathi.v
 

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